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BEST-AVAILABLE COPE June 12, 1923. 7 1,458,143 H. J. MULLER OPTICAL METHOD AND APPARATUS Filed June 8, 1920 31/ I T E I z 'vr'l'i'l li 1!! llllllllllllllll 55" 2 g I My ml llllllllllillllllll mmmlnlulnllwlwlvflllu [E 40/ 15:12 3 i I L I N VEN TOR.

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Patented June 12, 1923.

UNITED STATES HERMANN :r. MULLER, or NEW YoRK, not.

OPTICAL METHOD AP PARATUS.

1 Application filed June 8,

T all whom it may concern.

Be it known that I, IIICRMANN J. Mmirasn, a citizen of the United States, and resident of New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Optical Methodsand Apparatus, of which the following is a specification. My present invention relates to optical methods and apparatus. 1

An object of the invention is to provide one or more simple and dependablemethods which can be utilized to advantage for practicing any or all of the following arts: making microscopic photographs of tangible'objects, making magnified photographs of microscopic objects, making photographs of microscopic objects magnified and superposed upon tangible objects, making microscopic photographs of microscopic objects, treating localized areas of microscopic objects toany kind of light, performing measurements 'upon and making accurate and magnified sketches of microscopic organisms or other objects. v

Another object of my invention is to provide apparatus simple inconstruction and easy to operate-which. can be utilized with. maximum convenience for carrying outany or all of the above'arts,althomh apparatus.

of materially different character might be used with good results for this purpose' In the'speoificationandclaims I apply the term reversed or counter-micrography to cover generically the photographic processes above referred to, that is, making microscopic photographs of tangible objects,

making photographs: of microscopic objects magnified. and superposedupon tangible objects and -g'iiaking microscopic photographs. of objects of microscopic dimensions; The term tangible refersto objectsof dimensions easily visible with the naked eye as distinguished fiom microscopic objects.

The art above referred to of treating localized areas of microscopic objects with light of anych'aracter to theexclusion ofrthe rest of the microscopic object whichis kept substantially darkmay be practiced by my method even though the microscopic object has an irregular movement of its own, and the apparatus of my invention may be used in this relation whether 7 the microscopic object isstationary or movable. I

'By my flnvention, I practice allof'the above ar throughthe applicsition at a com 1920. Serial 1%. 387,286;

mon principle which I will term reversed.

microscopy. This consists broadly projecting light through a microscope in a reversed direction so as to produce an extremely reduced image either of an object or of some other source of light of a restricted size and definite pattern as the case may be, directly upon another object. The term reversed direction is from ocular to objective, which is the reverse of that in which light travels when the'microscope is used for ordinary magnifying purposes. To carry out this principle I prefer to employ an ordinary compound microscope which I dispose between the two objects or between the source of light and one object, adjusting the microscope so as to dispose the source of light or-the object which furnishesthe light at the focal plane, which is nearer the eyepiece and the other object on which the light is to be projected at the focal plane which is nearer the objective lens of the microscope. Thusit will be seen that a reduced image of the first. object or the source of direct lightas the case may be, will be-focused by the microscope 1n--,

superposed relation upon .the-; other object.

.Applying,this princip-le to the art of reversed micrography, microscopic photographs oftangible. obj ects. be made by disposing a vcompound microscope in, such position, that. light from. the. object enter its eyepiece and ,placing a photographicifilm or plate. adjacentxthe objectiveof the microscope so that light coming through the objective will fall upon it and: then adjusting the microscope until the obj ect and the film are: in complementary focal planes-and directing light of the proper intensity from the object through the microscope in reverse direction- (from eye-"-" piece to objective) to the film.-v Thelight normally reflected from the objectwill ordinarily be sufficient when focusediupon the smaller film to make the positive; In this way either a single negative or asu'ccession? of negatives of a moving object foramoving picture may-be obtained, In-the latter case, the moving. objectsis preferably kept in focus by the use-of a second microscope as described. subsequently. v V For the sake of conciseness, the focal plane lying outside of the microscope adj acent its objective lens will, be termed the objective olane and that lying outside, the. microscope nearer its eyepiece end Still.- beternidithe ocular pla ne. although it is, of course, understood that both ocular and objective lenses have other focal planes, inside the microscope, and also-that the so-called ocu lar plane may not be sensibly a plane but may have a very considerable depth. More over, when these planes are mentioned only those portions of the planes are referred to which are in such position that they could actually .receive light directed through the microscope;

In the treatment of a localized area of a iiiicroscopic' ohject withlight of any desired intensity while maintaining the rest' of the microscopic object substantially dark, it will he understood that the microscopic object and a-soul-ce of light of desired size and shape are disposed atc onjugate' focal planesof the microscope in'a manner analogous to that set forth abovefthe microscopic object lying in the objective plane and the source of light inthe ocular plane. The light in this case is preferably either projected through a pin hole'or otherhole of the desired size and shape formed in "a plate or sheet located in the ocular plane, or it is "reflected from a bright surface such as drop o'fm'e'rc'ury, which lies in this plane; so that a reduced image off thelum'inous hole or surface which maybe considerably smaller th'an'the size oi the microscopic object is projected in" reverse direction upon the microscopic 'ohje'cft which lies-in the objective plane. Th'e'lum'inous pinhole or drop will be the source of light for all practical urposes, and the adjustment described a ovc "is made with respect to said luminous hole or drop.

Tn measuring or drawing a microscopic object according to my method the micro- "in "the ordinary direction through another finicroscope, "the latt .r produces upon the retina *the eye 'amagnified image of the object witha superposed magnified image of the reduced image of the paper or scale.

The magnified image of the "microscopic dbect will, therefore, appear 'to the eye as superposedfupon substantially thenorinal sized sheet-oi? paper or scale'and the drawing or measurements can be readily made.

I'n-the preferred manner of executing all,

BEST AVAILABLE cot-"- of the above methods, asecond microscope ivill be provided disposed as in the case last described. \Vhile viewing a microscopic obect through ,the; second or magnifying microscope, the first or reducing .icroscope 'will be manually adjusted until an image of alignment with each other to act'in opposition, with their objectives facing each other, the first or reducing microscope being usually below" the second or magnifying microscope. Ingen'eral areducedimage of tangible object-or of a source of light is projected in reverse direction by the reducing microscope upon the film or microscopic object-which latter 'is preferably upon a slide mounted on a stage between the two microscopes. The up 361' microscope is-first focused upon the ob ect on the stage and then the lower microscope is manipulated until the image of the tangible object or source of light appears also in focus, when viewed throughthe magnifying microscope. lVhen this occurs it will be understood that the objector source of lightand the film or microscopic object are at conjugate focal planes of the lower or reducing microscope.

'It will thus be seen that-by the use of the second or magnifying microscope, I provide a convenient arrangement for-disposing conjugate focal planes of the first or'reducing microscope at the two objects.

\Vhen the focal adjustments have thus been made, the source of light or tangible object in the ocular plane m ay than "be moved about within this plane so'that its image will fall in precisely the desired position upon the microscopic object, and, if the latter moves, the object in the oculat plane may be moved correspondingly.

It will be understood that instead of using the above arrangement for viewing directly with the eye the enlarged image of the microscopic object together with the superposed image of the tangible object,these superposed images may be projected upon a photographic film-or plate lying 'in the ocular plane of the magnifying-microscope and thus a photograph of ordinary sis: will be produced of the large object with the small object superposed thereon, the latter greatly magnified.

It will be noticed thatwhen the two objects are at conjugate focal planes of the microscope the light from either one will be projected in focus upon the other For "this reason the same featureof the double microscope arrangement which facilitates l scopic photographs or superposed photo- 'graphs of the sort just described, facilitates also the making of the similar adjustments which are necessary for obtaining greatly magnified images and for making magnified photographs of microscopic olnects.

' This will be 'described in detail below under the heading f'operation.

Referr1ng now to the accompanyingdrain: 'ings', Fig. 1 shows my preferred form of apparatus for executing all of the methods mentioned except that of making microscopic photographs of microscopic "objects, :and Figs; 2, 3 and 4 are purely diagrammatic views indicating manncrsof executing "the-"methods, without the use of the appa- 'hiivi g "able support 4. Y 'Rigidly secured to the -sup- "port 1 by 'any 'd'esire'd means, there is a 'sta ge 5"g')f a construction common in micro rat'us shown in Fig. Fig. 5 is a diagrammatlc view illustratingmy preferred method 'of making microscopic photographs of microscopic objects:

Referring toFigQ 1, I have showna stand comprising a base 1 with upstanding lugs 2 pivoted; thereto "as at 3' fan adjust- ,sco'pes whichiie'ed' neitherlbe shown nor described ili'dtailf- The stage should be proyided upon; its 'uppei siirfa'cewith'clips (not shown). -to hold 'aslidi'bu't preferably has ndoth'er accessoryattachmentsl Secured to the'lsupport' rand to' opposite sides of the stage 5' I"prefer"to"pro vide a p'ai'r'of compound microscop'e hni ts 6" and 7 which may be o'fthefdrdinary Construction in common 1' s that -I 'wi11= cal] and the lower unitrespectively.v Briefly-,- the use. The apparatus is frfequently'used with the adjustable support" in *yertical-i position, h:e 1mits"6 and 7 'the upper upper or magnifying microscope 6 comprises an arm 8 having adjustably-connected there to; a tube 9 pi'oy id'ed"with-ant'eyepiece 10 at 'it's upper-end andan 'iobjective: .lens' 11 at the -'lower"'entl.'- 'jThe usual screw 12 is provided for 'mzikingcoarse "settings and the knurled head '13' for--makin'v"fine settinqs 4 through gearing of known construction (not T shown). The 'lower microscope 7 has pref- 'erably anobje'ctiv'e- 14 of thesameimagnifyling power'as theupperlmic'ro'scope and has it's objective facin'o th'estagefaand its eyepiece 15 at the provide the eyepiece 15 withi'a double concave lens 16 instead of the-usual convex lens; the purpose of '.'this-' construciiiwer'end. I: preferably tiori appearing clearly below. The eyepiece-"15' of"the-- lower microscope ma' i,

'howeve'ri'rbe' omitted entirely in operations in==Which especially clear definition rather than great? reduction of the-image rejected through theireduclng microscope 11s desirech :13'he terms ob ective smtfeye BEST AVAILABLE COP";

.these terms are. functionally inapplicable.

A stage or platform 17 preferably lies upon the base 1. 7 i

The arm of the lower microscope is preferably rigidly secured to the supporting base 4 by any desired means as shown at 18. The arm 8 of the upper microscope is preferably secured to permit slight shifting thereof in orderto dispose its optical axis into exact alignment with that of the lower unit. For this purpose the flanged base 19 of the microscope arm 8 is enclosed in a ring 20 secured to support 4: and havingan inturned rim 21 overlapping the'flange 19. Four set' screws two of which are shown at 22-23. pass through the lateral surface of the ring 20 and can be used for slightly shifting the arm 8 along the stage 5 to effect the alignment. Locking screws 24; passing through W the rim'21 in the ring will'clamp themicroscope unit 6 in adjusted'position. i

In making a microscopic photograph of a microscopic object,- the enlarged image I of the said object obtained in the "ordinary" Way through a magnifying: microscopebecomes the source of light'fortheoperation of producing-a microscopic:photograph .previously described, the light from the enlarged image being projected through-aictducing microscopeain the reverse: direction and focused upon WPlIOtOg'IEIPlllC film lying in the objectlve plane of the reducing microscope. The eyepiece of both microscopes maybe omitted in. this process; Operation? For making .-a:. :'microsc0pic photograph of a tangible'objectiby my pitcfer'red 'method and by the aid of the; :pre-

microscope. W'hen-t-h'is occurs itwill be understood thata reduced image ofithe'large object has been projectedby; the-lower microscope 7 into the plane of-the little-object.""1

The lower-microscope has-thus been setto dispose conjugate 'focal'planes one at the large object and the-other at the small object, and a small photographic film or plate may now be substituted for the small -ob-" ject, with its sensitive surface in the plane previously occupied by the small object ga ilarlr screen of any suitable constructionbeing used to-enclose the stage. The ordifiai ry daylight reflected froi in? the large db eot will given a rapid. and periodic hange of tion under the ob ective -microscopo by any automatrc device desired,

the negatiye from which printmay be mane in the usual manner.

If it is desired to make a microscopic moving picture, the photographic film "D0522- of. the reducingbeing at the same time held within the objectire plane. Li from. the ob; -must be cut oil froze the film while the is in motion and allowed t fall on it dur the interims when the film is at rest.

In order to malre a drawing of a microscopic object upon an enlarged scale by the use of the apparatus shown in Fig. 3.. a sheet of drawing paper is laid upon the stage 17, the magnifying microscope V6 is 21-1- justed to focus upon the microscopic obicct. and thereupon the lover microscope T will be adjusted until the paper is'seen sharply in focus through the eyepiece of the'upper microscope. It will he clear'that the lowermicroscope has projected a greatly reduced image of the paper onto the microscopic ohject and the upper microscope has-magnified this reduced image so that the two microscopes are or similar power, the paper will a magnified image of thereupon.

appear to the eyesubstentially full size with the microscopic object- VJith a pencil or pen the operator may then make the enlarged contouror detail drawing of the microscopic object upon the paper. observing the object, the paper, and the movement of his'hand and of the pencil through the eyepiece 10. Paintings. etchings, or other manual representations may be made in a similar u'ianner. such as may readily be understood from the foregoing account.

As the ordinary microscope produces an inverted image of an object difliculty would be experienced in tracing the outline. since the pencil or hand viewed through the eyepiece of the upper microscope would appeasto move in a direction opposite to the actual movement. It is for this reason that the double concave lens is used. in the eyepiece of the lower -microscope. This double concave lens inverts the image lyingin the objective plane whereas the usual convex lens eyepiece does not. The additional inversion thus effected will obviously result in the formation of erect images of the paper, the pencil and the movement of the latter when 0 -viewed through the microscopes in'series. It

may be noted that the double concave lens has the further important advantage of giving a larger field O1. vision than would a convex lens. It will be understood that other means such as a prism could be used BEST AVAILABLE CDP\ for rectifying the imige of the object lying on platform 17, but preter to employ the specific arrangement shown and described.

In order to perform measurements upon a microscopic object by the use of the apparatus shown inFig. 1, an ordinary scale would be substituted for the sheet of paper upon the platform 11' and upon focusing the image of the scale upon' the microscopic objectby the method set forth above, it will he apparent frozutheabovethat'the scale will appear of ordinary size.',.if ..the two microscopes are or equal power and the microscopic object will appear superposed thereon in greatly magnified form. luorder to obtain the true dimensions of the microscopic object the readings taken upon the scale will, of course, have tobe divided by the magnifying ratio ofthe lower or reducing microscope which ratio may "easily be determined by substituting for the microscopic object to be measured another microscopic object of known size and obtaining its apparent measure on the ordinary scale. r. v

Although I preferto employ microscopes having objectives of equal powers .for the above purposes, it is notessential to do so. It" the powers -be diflerent .the image of the paper or of the. scale will appearto the eye as somewhat reduced :;or somewhat enlarged with respect to its dimensions when viewed with the naked eye such adjustments of the difierences in magnification', however, are usuallysecured more efiiciently by adjustment of the power of: the eyepiece 15 of the reducing microscope. V

In order touse the apparatus shown in Fig. l for the purpose of subjecting a localized area of a microscopic object to the influence of light there will be substituted :for the paper shown in Fig. 1 a plate or sheet having therein a bright spot of light such as may be produced by a pinhole or other hole of the shape corresponding to that of the localizediarea to be illuminated and of a size as many times larger than that area as the magnifying ratio of the lower or reducing microscope. A light is placed back of the plate or sheet and r'ys, pass therefrom through the hole. Alternatively to the pinhole, a bright object such as a drop of mercury with light thrown upon it may be used. The image of the luminous pinhole or other opening in the sheet on the lower platform will be focused upon the microscopic object on the stage in the manner obvious from the above and the plate or sheet can be manually moved until the illumination is accurately centered upon the selected region of the microscopic object which is to be treated. If the microscopic object has no proper movement the plate or sheet with the pin hole is prefer-ably black. It will be obvious that infra-red or ultrait lies.

violet rays may be employed instead of the visible rays either in the operation of treating a localized area f a microscopic object or in making a microscopic photograph, provided the lenses of the focusing microscope are made of a substance permeable to the rays.

In order to makethe adjustments necessary for disposing the microscopic object or the film and the source of invisible light in conjugate focal planes and in the desired positions with relation to each other it will be desirable first to adjust the microscopic object or, the film for a visible source of light in the manner previously described, focusing upon the microscopic object or film a greatly reduced image of the visible source, said image having the same size, shape and position with respect to the microscopic object as that desired for the image ofthe invisible source. Thesource of invisible light identical in pattern with that used -forthe visible light may then be substituted for the source of visible light, with duechange in adjustments necessitated by the difference in refraction between the two kinds oflight. Such readjustments may be made in the following manner: A piece of cross-ruled paper (coordinate paper) having the lines numbered is placed in the ocular plane, and the source of visible light is disposed so as to be projected in the desired fashion upon the microscopic object. A diagram of the shape, size and position of the source of light is then made upon the coordinate paper in'the position in which For this coordinate paper is now substituted another piece of coordinate paer having the cross-ruled lines spaced differently, with the spaces so proportioned relatively to the spaces on the first paper that when the second paper is substituted for the first and when the invisible light is substituted for the visible and the change in focus made, the images of given lines on the second paper will fall upon the same places in the objective planes as the corresponding lines in the first coordinate paper previously fell. The source of invisible light is now constructed so that it will have the same position relative to the lines on this second paper that the source of visible light had to the lines on the first paper. The change in focus is made by turning the screw of the fine adjustment through a known distance measured on a graduated are adjacent the screw. The distance required will have been previously determined by testing. out the difference in focusing adjustment necessary for bringing the invisible light from a given objective plane into focus in the same ocular plane as that in which the visible light from the same objective plane was previously focused.

In subjecting a localized area of a micro- BEST AVAILABLE com sccpic object to visible light, if the microscopic object has a proper movement, it is preferable to employ a somewhat illuminated plate or sheet in which the pin hole or other bright area is formed or a sheet of a different color from that of the light with which the object is to be treated. The entire microscopic object will then be faintly visible or visible with the different colored lightthrough the eyepiece 10 and the light from the bright area will be sharply focused upon the localized area to be treated. As the microscopic object moves the slightly iliuininated plate is followed up with the hand to maintain the intensive light upon'the selected area. Y i

In thecase of any of the above operations with visible light, the microscopic object, particularly if in the form of a-unicellular organism may move upwardly or down? vsardly out of the plane upon which the microscopes are focused. This motion thou h through small distances can destroy "the focus of the apparatus. LIn 'order to rapidly reestablish the focus under this condition the knurled head 13 of the upper microscope will he turned slightly in the appropriate direction to again produce a sharp outline of the object. Preferably the lower microscope is so interlocked with the upper that it need not be separately manipulated for the corresponding adjustment which is nec-' cssary for it. For this purpose the knurled head of the upper microscope is' connected by-a rigid bar 26 with the knurled head 13 of the lower microscope so that any slight displacement made upon the upper microscope will be simultaneously imparted to the lower microscope. Thus, if the organism moves upwardly a slight amount, both can be correspondingly moved in unison with each other, to reestablish the condition of focus. An alternative method is to have an adjustable stage, preferably with a coarse and fine adjustment, such as that provided upon man} metallurgical microscopes, and instead of moving the microscope to move the stage in exact compensation for the upward or downward movement of the microscopic object.

In using the arrangement of two microscopes for facilitating the making of magnified photographs of microscopic objects, previously referred to, the following procedure is adopted: A sheet of paper is first placed in the ocular plane of the reducing microscope, and by the method previously described its image is made to fall in the desired position upon the microscopic object, which is in the objective plane between the two microscopes. A photographic film may then be substituted. for this sheet of paper, surrounded by a dark enclosure, and a source of illumination may be substituted near the ocular of the magnifying microscope to take 7 be encounteredin projectingand focusing .a darkened the place oil the eye of the observer. The direction of the light ,thus becomes entirely reversed, and it travels in a reversed dime-- tion from eyepiece to objective, through What waspreviously the magnifying microscope, to be condensed upon the microscopic object for purposes of illumination. From the microscopic object the light then proceeds in. the ordinary direction through what was prcviously the reducing microscope, tobe focused as a greatly magnified image upon the photographic plate. This method avoids the difiiculties which would the enlarged image upon a screen it also renders the focus more delicate than could readily be e'flected by the use of a screen, and moreover z'iyoids the necessity for the use of I enclosure about said screen. The optiin u iin'ode of illumination to be usedin 'tlie place of the eye after the substitution o f 'th'e filriirfor the paper is made, may previously have been determined by testing for the bestillumination through the a lane red cing m icrcscope while making the observation withth'e eye. This same arrangeme'ntior ill'umination is now transferred from the ocular planeof what was previously the reducing microscope, to be projected in ,s imil arinanner from the ocular plane of reviously the magmfymg micro- Wlat was p' g .U v

In those departments of reversed micrography \vhen microsc0pic photographs are made a specially -thin of particularly fine"grain, such as 'ina'ybe secured by the socall'ed albumin manta is preferably emp y In making microscop c photographs of microscopic'objects according to the method ,tion or reduction of the representation of tlie micr'osc'opic object'in, the microscopic photograph may be effectech The following shows how the preliminary step in the practice of the various acts set 'fo1 th, which consists in disposing two obec't's. or. one object and a source or light at conjugate focal planes can be carried out 'rvitlioutthe use of the preferred apparatus'ofFi'g. 1. Place the microscopic obon slide :upon the stage of the microscopeand bii'rig s aid object'i'nto focus in BEST AVAILABLE COP\ magnified Image is produced thereon. The slide and the screen are noivin conjugate focal pla'r'ies. I

In Fig 2 'ijs 's'hou-n, purely diagrammaticall'y theapparatus for performiiig the steps just le'scribed H The microscopic bbj'ct is shpyyfn at 30, upon 'afs lide 31,fthe microscope appears 'at 32,"tlie light'at 33', the screen a't'ae i t e' ii e d. mage a 1 Conjugate "focal pit-resin regeneratmined as sh-own in Fi 2, 'm si p i as, indicated in'lhg. 4; 1;; Fig. & a tangible obj eot 34* been substituted for the screen of Fig. 'a photographic film 30 ina dark enclosure "For the slide or inicroscbp'ic object. The microscope 'thus' throws a greatly reduced image of the tangible'obj'et upon the photographic film, and a ave;

noted i'n the'descriptiohiiffthe racti'ce of this art iviththe' apparatus of -1 no sep'ar'iite septaor illiimir'iation 'isnee'dd.

The processof subjecting a selected localiZe'd area of a microscopieobjeetto the iiifiucnce of light may be carried out apart from the apparatus Io'f Fi'g, Iffi's shown 'for" instance in'Fig. 3. The-rennet o'f'the pelts in practicing 'this 'art 'c'an be} identical that "shown in Fig. 2 "except that 3& represents "a black screen c'ontainii ig a pin hole, a drop of mercury or'otliendesiied source of light which is substituted for the 'white screenof'Fig. 2 ."the 's'o'iir'ee of light having been placed at the 'spot'39 in the "imagej'of the tangible "object corresponding "to the spot to be treated in the microscopic object. The light is now projectedthrough'the microscope 32 11 1011 the desired localized area 27 "of the microscopic object. "It 'isfiinden stood that not only a small spot ofl-ight but any pattern orthe imagefo'f a tangiblepbject may thus be'projecte'd inp'reciselythe desired spot upon any exposed portion of the microscopic object.

In'Fig. 5 is shown an arrangement for makin microscopic photographs'of microscopic objects. he microscopic "object or slide is -shown a t '80 and'its enlarged image formed bv the first or magnifying microscope 40 is shown at' 3-5:- A second-or reducing microscope 411 is optically alignea with microscope' iO 'and'servs to projecta reduced image 37 of the magnified image 35 upon the film 42. The film is of course placed in a plane conjugate to that of the enlarged image with respect to microscope i1 and this by any of the methods set forth.

It will be understood that the preferred form of apparatus shown in Fig. l is not limited in its application to the specific uses described above.

I claim 1. The method of reversed microscopy which consists in projecting light from a source of the character described through a compound microscope, in the reverse direction upon a microscopic object lying in the objective plane, with the resultant superposition upon the microscopic object of a greatly reduced image of the source of light.

2. An optical instrument comprising a support carrying a stage and two microscope units on opposite sides of the stage and in axial alignment with each other, said microscopes being arranged with their magnifying powers in opposition.

3. An optical instrument comprising a support carrying a stage, a microscope unit upon said support and to one side of said stage, a microscope unit u on said support and to the opposite side 0 said stage, said units being axially aligned with each other and having objectives facing said stage.

4L. An optical instrument comprising a support carrying a stage, a microscope unit secured to said support below said stage, a microscope unit secured to said support above said stage, said units having objectives facing said stage, said units being slightly adjustable relative to each other to dispose their optical axes into accurate alignment.

5. An optical instrument comprising a supporting stand, a stage mounted thereon, a microscope unit having an arm secured to said stand below said stage and having an objective facing said stage, a second microscope unit with an objective of the same power as said first unit having an arm secured to said stand above said stage and having an objective facing said stage, and means permitting slight shifting of said upper arm to accurately align the opticalaxes of said units.

6. The method of exactly adjusting the position of a greatly reduced image of a source of light upon any desired portion of a film or microscopic object, which consists in observing said image and film or microscopic object in their superposed, or nearly superposed relationship, through a magnifying microscope, and meanwhile manually altering the positions of the source of light,-

the microscopic object, or the reducing microscope, until the reduced image is observed to fall in the desired position upon the film or microscopic object.

7. An optical instrument comprising a supporting stand, a stage mounted thereon, two microscope units mounted thereon at opposite sides of said stage and having objectives facing said stage, one of said units being constructed to produce an erect image and the other to produce an inverted image.

8. An optical instrument comprising a supporting stand, a stage mounted thereon, two microscope units mounted thereon at opposite sides of saidstage and having objectives facing said stage, the eyepiece of one of said units including a convex lens and that of the other a double concave lens.

9. An optical instrument comprising a supporting stand, a stage mounted thereon, two microscope units mounted thereon, with objectives of equal power, one above and the other below said stage, and having objectives facing said stage, the eyepiece of one of said units including a convex lens and that of the other a double concave lens, the latter unit having a greater ratio than the former.

10. The method of maintaining a greatly reduced image of any visible source of light in focus upon the plane of a microscopic object or film that has a motion in a direction parallel with the axes of the microscopes, which consists in first projecting through a reducing microscope a greatly reduced image of said source upon the microscopic object orfilm and viewing said object or film together with superposed reduced image through a magnifying microscope axially aligned with the reducing microscope, meanwhile continually moving the stage carrying the microscopic object along the optical axis so that said object appears continually in clear view.

11. An optical instrument comprising a support carrying a stage, two microscope units on opposite sides of the stage and in axial alignment with each other, said units having objectives facing said stage, said units having each a coarse adjustment means, and a fine adjustment means, and said stage having a fine adjustment means.

12. An optical instrument comprising a microscope having an eyepiece, an objective and a stage for supporting a microscopic object, and focusing means for projecting an image of an external body upon said microscopic object.

13. An optical instrument comprising a support carrying a stage, two microscope units on opposite sides of the stage and in axial alignment with each other, said microscopes being arranged with their magnifying powers in opposition, and means connecting said units for adjustment thereof in unison.

14-. An optical instrument comprising a support carrying a stage, a microscope unit upon said support and to one side of said stage, a microscope unit upon said support and to the opposite side of said stage, said units being axially aligned with each other and having objectives facing said stage, said BEST AVAiLABLE COP.

units having each a coarse adjustment means, and a fine adjustment means, and a rod connecting said fine adjustment means for operation thereof in unison.

15. The method of making a magnified picture which consists in projecting througha reducing microscope a greatly reduced image of a pictorial surface and an instrument, upon a microscopic .object and tracing with said instrument a magnified picture of said object While viewing said object with the superposed image of said surface and instrument through a magnifying microscope.

16. In apparatus of the character described, in combination, a stand, a stage mounted thereon, two microscope units mounted thereon 011 opposite sides of said stage -and having objectives facing said stage, a translucent plate having a small opening therethrough disposed adjacent the eyepiece of one of said microscopes, and a light arranged to project a beam through said hole and through the adjacent micro scope to he focused upon said stage.

Signed at city of Kev: York, in the county of New York and State of New York, this fifth day of June A. D. 1920.

H-ERLLXNN J. MULLER. 

